Rheostat.



I PATENTED JUNE 27, 1905. W. 0. YATES & A. M. FENWIGK.

- RHBOSTAT.

APPLICATION FILED SEPT. 26, 1904.

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I MT ESSESI v UNITED STATES Patented June 27, 1905.

PATENT OFFICE.

WILLIAM C. YATES AND ALEXANDER M. FENWICIQOF SCHENECTADY, NEW YORK,ASSIGNORS TO GENERAL ELECTRIC COMPANY, A COR- PORATION OF NEW YORK.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent N0. 793,493, dated June 27,1905.

Application filed September 26, 1904. Serial No. 225,877.

To ftZZ whom it may concern;

Be it known that we, WILLIAM C. YATES and ALEXANDER M. FnNwIoK, citizensof the United States, residing at Schenectady, in the county ofSchenectady, State of New York, have invented certain new and usefulImprovements in Rheostats, of which the following is a specification.

This invention relates to the control of electric motors; and its objectis to provide a rheostatic starting device for a shunt-wound electricmotor which shall be simple, compact, and inexpensive and so designedthat the parts interlock to make the device foolproof.

Our invention is particularly applicable to devices for starting largeshunt-Wound electric motors in which it is not desired to break themotor-circuit at the rheostat-contacts because the contact-surfaceswould be pitted by the spark formed when the circuit is broken; but itmust be understood that the principles of the invention are applicableto rheostatic controlling devices for motors of all sizes and tospeed-regulating rheostats, as well as starting-rheostats.

The novel features of our invention will be definitely indicated in theclaims appended hereto.

The details of construction and the mode of operation of our improvedrheostatic controller will be better understood by reference to thefollowing description, taken in connection with the accompanyingdrawings, which show the preferred embodiment of our invention, and inwhich Figure 1 is a front View of the panel; Fig. 2, an enlarged detailview of one of the circuit-breakers; Fig. 3, an enlargedelevation of thefield-switch, and Fig. 4 is a diagram of the circuits.

Referring to the drawings, 1 indicates a panel of soapstone, marble, orother insulating material, preferably supported in an upright positionby suitable standards, on which is also secured a subpanel carrying theresistance. Mounted on the panel are two circuitbreakcrs 2 and 8. Thebreakers shown in the drawings are of a standard type well known tousers of electrical apparatus and consist of a pivoted switch-bladecooperating withsuitable contacts and operated by a handle 4 and a latch5 for holding the blade in the closed position, provided with a handle 6for tripping the latch. Each breaker is provided with an overload-coil 7which in response to a predetermined overload draws up'aplunger 8,provided with a projection adapted to en' gage the latch 5 and trip thebreaker. One of the breakers is provided with a no-voltage coil 9,suitably incased, which on failure of the line voltage or when thecircuit is opened allows its core to drop and rock a pivoted lever 11 totrip the latch 5. Pivotally mounted on the panel is a switch-arm 12,carrying a blade 13, in the path of movement of which is a series ofcontact-plates 14, arranged in the arc of a circle. Switch-clips 15 aremounted on the panel in position to be cross-connected by the blade 13when the switch-arm is in the final position to out out of circuit allthe resistance. Pivoted in an opening in the panel is a lever 16, whichis engaged by the switch-arm when on the first contact-plate of theseries 14 to move a rod 17 in guides 17 on the back of the panel to aposition in which an opening in the rod (indicated by the dotted circlein Fig. 1) is in alinement with a projecting stud 18, adjustably securedbya set-screw 19 in an opening in the circuit-breaker 2. When theswitch-arm 12 is moved away from the first contact-plate 14, a spring18, having one end attached to rod 17 and the other to a post on theback of the panel, tends to move rod 17 in its guides to carry theopening in rod 17 out of alinement with the projecting stud 18, so thatif the blade 13 is out of engagement with the lever 16 and the breaker 2is open the breaker cannot be closed, as the projection thereon wouldengage the rod 17, and thus prevent the breaker from being thrown in farenough to close the circuit.

Mounted on the panel below the circuitbreakers 2 and 3 is a switch forthe motorfield. This 'switch consists of two parallel blades 20, pivotedin clips 21, mounted on the panel and connected at their ends by acrossbar 23, of wood or other insulating material. Switch-clips 22 arealso mounted on the panel in position to be engaged by the blades 20.Secured to or integral with the blades 20 and at right angles theretoare blades 24, which are connected at their ends by across-bar 25, ofinsulating material, similar to the bar 23. No handle is provided onthis switch. Instead it is operated by a switch which interlockstherewith and controls the circuit of the novoltage release-coil 9.Mounted on the panel between the clips 21 is a switch-clip 26, somewhatlonger than clips 21, and a switch-blade 27 is pivoted in this clip andextends out between the cross-bars 23 and 25. Mounted on the panel is aswitch-clip 28, of about the same length as the clip 26, in position tobe engaged by the blade 27, and an operating-handle 29 is provided onthe end of blade 27. The armature 30 of the motor is connected to thesupply-mains through the breakers 2 and 3 and so much of the resistanceconnected to the contact-plates 14: as is cut into circuit by the blade13. The motor-field 2,1 is connected to the switch-clips 21, and theclips 22 are connected to the lines above the breakers 2 and 3. Theno-voltage release-coil 9 and a resistance 32 in series therewith areconnected across the lines through the blade 27.

The operation of the device will be readily understood from theforegoing description. Then the motor is not in operation, the breakers2 and 3 are open and the switch-blades 20 and 27 are out of clips 22 and28, respectively. In starting, the circuit of the motor-field should beclosed first. If it is attempted to close the armatu re-circuit withoutfirst closing the field, the breaker 3 may be thrown in and will be heldby its latch 55, thus closing one side of the armature-circuit. Theother side, however, cannot be permanently closed, for if breaker 2 isthrown in the latch 5 will not catch, as the circuit of the no-voltagereleasecoil 9 is open and the lever 11 will beheld by the core 10 of theno-voltage release in a position to prevent latch 5 from holding thebreaker in, and the switch 27 for the no-voltage release-circuit cannotbe closed without closing the field-circuit. Thus the armaturecircuitcannot be closed before the field-circui t except by the operatorintentionally closing the field-switch otherwise than by handle 29 andblade 27 or by holding the breaker 2 in. To properly start the motor,blade 27 is turned on its pivot by the handle 29 and engages crossbar23, thus pushing the blades 20 into clips 22 and closing thefield-circuit. On further movement of the handle 29 blade 27 enters theclip 28 and closes the circuit of the no-voltage release-coil 9, whichraises its plunger, and thus permits lever 11 to move out of engagementwith the end ol latch 5. The armature-circuit should then be closed bythe breakers 2 and 3. 'When the armature-circuit is closed, theswitch-arm 13 for regulating the resistance should be on the firstcontact-plate 14, so that all of the resistance is included in circuitto cut down the cur rent admitted to the motor-armature immediately atstarting. If the blade 13 is not onv the first contact, the rod 17 isdrawn to such a position by spring 18 that the opening therein is out ofalinement with the projection carried by the breaker 2, and the breakercannot be closed. WVith the field-circuit of the motor closed and blade13 on the first contactplate 14 the breaker 2 can be closed, thusstarting the motor. Switch-arm 12 is then turned on its pivot, movingblade 13 over the contactplates 14 to cut resistance out of thearmature-circuit. and thus bring the motor up to speed until it reachesits final position, where it engages clips 15 and connects the armaturedirectly across the lines. In event of an overload, coils 7 on thebreakers draw up the plungers 8 and open the breakers to open thearmature-circuit. .ln event of an under-load or of an opening of thecircuit core 10 falls, rocking lever 11 and latch 5, and thus openingthe circuit at the ln'eaker 2. In either case the spring 18 moves rod 17in its guides to prevent the armature-circuit from being closed againwithout first bringing the rheostat-arm 13 around to the first position.The armature-circuitmay beintentionally opened by pressing the handle 6on latch 5 of either of the breakers. The field-circuit of the motor,however, cannot be opened while the armature circuit is closed. Itswitch-blade 27 is pulled out by means of handle 29, circuit through theno-voltage releasecoil 9 is opened as soon as the blade leaves clip 28,and the release-coil opens breaker 2 immediately. Further movement ofblade 27 brings it into engagement with cross-bar 25, and thus forcesthe blades 20 out of the clips 22 to open the field-circuit. Thus thearmature-circuit of the motor cannot be permanently closed before thefield-circuit is closed, the field-circuit cannot be opened until afterthe armature-circuit is opened, and the armature-circuit cannot beclosed except when the switch-arm I3 is on the first contact-plate let,in which position all of the resistance is cut into thearmature-circuit.

It will be evident that many modifications can be made in the design andconstruction of our improved rheostat without departing from the spiritof the invention.

Such modifications of the controlling-device illustrated and describedherein we consider within the scope of our invention, and we aim tocover them in the claims appended hereto.

hat we claim as new, and desire to secure by Letters Patent of theUnited States, is

1. The combination of a motor, a switch for closing the armature-circuitthereof, an adjustable resistance in the armaturecircuit,

ITO

means preventing closure of said switch unless all the resistance is incircuit, means for closing the fieldcircuit of the motor, and meanspreventing opening the field-circuit before the armature-circuitisopened.

2. The combination with an electric motor, of a circuit-breaker forclosing the armaturecircuit thereof, a low-voltage release devicetherefor, means for closing the circuit of the low-voltage releasedevice, and means for closing the field-circuit of the motor arranged toinsure closure of the field-circuit before the circuit of thelow-voltage release device is, closed.

3. The combination with an electric motor, of a circuit-breaker forclosing the armaturecircuit thereof, a low-voltage release devicetherefor, means for closing the circuit of said device, and means forclosing the field-circuit of the motor arranged to insure opening thecircuit of said release device before the fieldcircuit is opened.

4:. The combination with an electric motor, acircuitbreaker for closingthe armatu re-circuit thereof, and a low-voltage release device for thebreaker, of a switch for closing the field-circuit of the motor, and aswitch -interlocked therewith for closing the circuit of saidlow-voltage release device.

5. The combination with an-electric motor, a circuit-breaker for closingthe armature-circuit thereof, and a low-voltage release device for thebreaker, of a switch for closing the field-circuit of the motor, and aswitch for 7 closing the circuit of said low-voltage release deviceinterlocked to insure closure of the field-circuit before the circuit ofthe low-voltage release device is closed.

6. The combination with an electric motor, a circuit-breaker for closingthe armature-circuit thereof, and a low-voltage release device for thebreaker, of a switch for closing the field-circuit of the motor, and aswitch for closing the circuit of said low-voltage release deviceinterlocked to prevent opening the fieldcircuit before the circuit ofthe low-voltage release device is opened.

7. The combination with a motor, of a circuit-breaker for closing thearmature-circuit thereof, a low-voltage release device for saidcircuit-breaker, an adjustable resistance in the armature-circuit, meanspreventing closure of the breaker unless all the resistance is inc1rcuit, a switch for closing the field-circuit, and

